If purchasing to store for a long period of time, 'cheap' and 'humidor' should never be in the same sentence, that is unless you make one yourself (which is a great idea) if you don't care about how it looks. A 'cheap' humidor will do, if you want to keep your cigars for under about six weeks, and you smoke them really quickly. If you wish to put some age on the cigars, get something quality.
Think of it this way... If you keep 30 $50 cigars, you have invested $1500. Why would you want to keep your investment in something 'cheap' that will not protect them? Further, always purchase a humidor that holds a greater capacity than the amount of cigars you wish to store. Allowing different 'types' of cigars to touch can cause the flavors to meld, so it is always a good idea to keep them separated if possible.
As someone brought up earlier, a humidor made from a seal able cooler will work as good (if not better) than any store bought one. Here is a great link on how to make a few different types.
http://www.stogiefresh.com/buildyourown.htm
If you decide to purchase one, PLEASE, PLEASE, PLEASE, properly condition it prior to using it. In my experience that takes about a week to do. Always use DISTILLED WATER. Tap water will fuck your stogies faster than anything else. Remember to open your humidor for a couple of minutes once a week as well, so there can be airflow.
My final suggestion is to buy about a dozen really cheap cigars off the start to practice with. Southern Ontario has really difficult conditions to keep moisture levels regulated in. Very low humidity in the winter, and far too much in the winter.
Jerry or Shawn at Cigar Studio
http://www.cigarstudio.com/ are EXCELLENT people to talk to. Super nice, great customer service, and will get you set up with something to your liking in a very decent price range, and will not do a hard sell or over sell. I have been going there for years, and they are the people I trust.
Hope this helps a bit.